1. Field of the Invention
The present invention relates to an image forming device such as a printer, copying machine, MFP, or the like.
2. Background Information
In recent years, an image forming device such as a printer, copying machine, MFP or the like has been widely used in not only offices, but in homes as well. FIG. 1 is an external view of such image forming device. These types of image forming devices typically include a paper supply cassette 1 and manual feed tray 2 as shown in FIG. 1.
In other words, the paper supply cassette 1 stores paper determined by a user in advance such as A4 size or the like (standard paper), and the paper is supplied to the printing unit from the paper supply cassette 1 when using the paper. The part which performs the supply operation is called the main unit.
Conversely, when printing on paper that differs from standard paper, i.e., special paper such as a post card, OHP film, or the like, a user opens the manual feed tray 2 (indicated by the arrow A) and inserts the special paper into this manual feed tray 2. The part which performs the operation in which paper is supplied from the manual feed tray 2 to the printing unit is called the bypass unit. In addition, when printing is performed without using special paper, the manual feed tray 2 is preferably closed (arrow B) in order to protect the image forming device from dust.
In view of the demand for energy savings, there have been demands in recent years for the development of technology that can conserve power consumption to the maximum extent in this type of image forming device. Such energy saving technology is disclosed in Japanese Laid-Open Patent Publication 2003-233276. This technology switches to power save mode when paper cannot be detected or when a user is not present around an image forming device.
However, there are the following problems with the technology in the aforementioned reference.
First, switching to power save mode when paper cannot be detected because paper has run out during a print job of multiple images is not suitable, as the user is most likely to replenish the paper supply immediately and resume printing. This is especially the case if switching to power save mode when running out of paper while the user is away from the image forming device, as the heating roller of the fusing unit will need to be re-heated to resume printing and this requires additional time.
Further, a plurality of sensors to detect the absence of a user must be provided for switching to power save mode when a user is not present around the image forming device, thereby causing the circuit design to become complicated and expensive.
An object of the present invention, having given consideration to such problems, is to provide an image forming device that reliably detects whether a user is to use the image forming device or not, and has the ability to conserve power consumption with an inexpensive and simple design.